PROPELLER FLOW FIELD ANALYSIS BY MEANS OF LDV PHASE SAMPLING TECHNIQUES

Two phase sampling techniques ore developed for the analysis of a propeller wake flow field by LDV. The first follows the basic approach of phase averaging by angular triggering, with some enhancements to improve measurement efficiency. The second procedure uses the particle crossing the LDV measurement volume to trigger the acquisition; each sample, tagged with the blade angular position at the measurement time, is then arranged inside angular slots. The implemented techniques prove to be complementary from the accuracy and efficiency point of view. The angular triggering technique allows accurate and spatially detailed investigations in the turbulent blade wake and tip vortex flows, also providing useful information in cavitation prediction. The tracking triggering technique is instead useful for routine in wake evolution analysis, in view of the minimization of data acquisition time.